The search for new therapeutic agents has been greatly aided in recent years by better understanding of the structure of proteins and other biomolecules associated with target diseases. One important class of these proteins is the sigma (σ) receptor, a cell surface receptor of the central nervous system (CNS) which may be related to the dysphoric, hallucinogenic and cardiac stimulant effects of opioids. From studies of the biology and function of sigma receptors, evidence has been presented that sigma receptor ligands may be useful in the treatment of psychosis and movement disorders such as dystonia and tardive dyskinesia, and motor disturbances associated with Huntington's chorea or Tourette's syndrome and in Parkinson's disease (Walker, J. M. et al, Pharmacological Reviews, 1990, 42, 355). It has been reported that the known sigma receptor ligand rimcazole clinically shows effects in the treatment of psychosis (Snyder, S. H., Largent, B. L. J. Neuropsychiatry 1989, 1, 7). The sigma binding sites have preferential affinity for the dextrorotatory isomers of certain opiate benzomorphans, such as (+)SKF 10047, (+)cyclazocine, and (+)pentazocine and also for some narcoleptics such as haloperidol.
The sigma receptor has at least two subtypes, which may be discriminated by stereoselective isomers of these pharmacoactive drugs. SKF 10047 has nanomolar affinity for the sigma 1 (σ-1) site, and has micromolar affinity for the sigma (σ-2) site. Haloperidol has similar affinities for both subtypes. Endogenous sigma ligands are not known, although progesterone has been suggested to be one of them. Possible sigma-site-mediated drug effects include modulation of glutamate receptor function, neurotransmitter response, neuroprotection, behavior, and cognition (Quirion, R. et al. Trends Pharmacol. Sci., 1992, 13:85-86). Most studies have implied that sigma binding sites (receptors) are plasmalemmal elements of the signal transduction cascade. Drugs reported to be selective sigma ligands have been evaluated as antipsychotics (Hanner, M. et al. Proc. Natl. Acad. Sci., 1996, 93:8072-8077). The existence of sigma receptors in the CNS, immune and endocrine systems have suggested a likelihood that it may serve as link between the three systems.
In view of the potential therapeutic applications of agonists or antagonists of the sigma receptor, a great effort has been directed to find selective ligands. Thus, the prior art discloses different sigma receptor ligands.
International patent application WO 91/09594 generically describes a broad class of sigma receptor ligands some of which are 4-phenylpiperidine, -tetrahydro-pyridine or -piperazine compounds having an optionally substituted aryl or heteroaryl, alkyl, alkenyl, alkynyl, alkoxy or alkoxyalkyl substituent on the ring N-atom. The terms aryl and heteroaryl are defined by mention of a number of such substituents.
European patent application EP 0 414 289 A1 generically discloses a class of 1,2,3,4-tetrahydro-spiro[naphthalene-1,4′-piperidine] and 1,4-dihydro-spiro[naphthalene-1,4′-piperidine] derivatives substituted at the piperidine N-atom with a hydrocarbon group alleged to have selective sigma receptor antagonistic activity. The term hydrocarbon, as defined in said patent, covers all possible straight chained, cyclic, heterocyclic, etc. groups. However, only compounds having benzyl, phenethyl, cycloalkylmethyl, furyl- or thienylmethyl or lower alkyl or alkenyl as the hydrocarbon substituent at the piperidine nitrogen atom are specifically disclosed. The compounds are stated to displace tritiated di-tolyl guanidine (DTG) from sigma sites with potencies better than 200 nM. 1′-benzyl-1,2,3,4-tetrahydro-spiro[naphthalene-1,4′-piperidine] is mentioned as a particularly preferred compound.
European patent application EP 0 445 974 A2 generically describes the corresponding spiro[indane-1,4′-piperidine] and spiro[benzocycloheptene-5,4′-piperidine] derivatives. Again the compounds are only stated to displace tritiated di-tolyl guanidine (DTG) from sigma sites with potencies better than 200 nM.
European patent application EP 0 431 943 A relates to a further extremely broad class of spiropiperidine compounds substituted at the piperidine N-atom and claimed to be useful as antiarrhythmics and for impaired cardiac pump function. The said application exemplifies several compounds, the majority of which contain an oxo and/or a sulfonylamino substituent in the spiro cyclic ring system. Of the remainder compounds, the main part has another polar substituent attached to the spiro nucleus and/or they have some polar substituent on the piperidine N-atom. No suggestion or indication of effect of the compounds on the sigma receptor is given.
Patent applications EP 518 805 A and WO 02/102387 describe sigma receptor ligands having piperidine or spiropiperidine structures.
With regard to the chemical structure of the compounds described in the present patent application, there are some documents in the prior art which disclose pyrazole derivatives characterized, among other things, for being substituted by amino alkoxy groups in different positions of the pyrazole group.
U.S. Pat. No. 4,337,263 discloses 1-aryl-4-arylsulphonyl-3-amino propoxy-1H-pyrazoles, wherein the amino group can be constituted by an N-cycle group as morpholine, piperidine or pyrrolidine group. They are used as hypolipemiant or hypocholesteroleminant agents.
Patent FR 2301250 describes similar compounds as those mentioned above, such as 1,4-diaryl-3-aminoalkoxy pyrazoles, wherein the amino group comprises pyrrolidine, piperidine, hydroxypiperidine, morpholine or piperazine derivatives.
Patent application US2003/0144309 refers to pyrazoles with their 3 position substituted by a dimethylaminoethoxy group and present in their 4 position a pyrimidine group. They are used as inhibitors of JNK3, Lck or Src kinase activity.
International patent application WO 02/092573 describes substituted pirazole compounds as inhibitors of SRC and other protein kinases.
International patent application WO 2004/017961 discloses pyrazole compounds wherein the 3 position is substituted by an alkoxy group directly bounded to a cyclic amide, which are used for therapeutically treating and/or preventing a sex hormone related condition in a patient.
U.S. Pat. No. 6,492,529 describes pyrazole derivatives which are used for the treatment of inflammatory diseases. These compounds present in the 5 position a urea group, linked in some cases to a morpholine ethoxy group.
International patent application WO 04/016592 refers to pyrazole compounds for inhibiting protein prenylation which comprises in the 5 position, among others, an alkoxy group directly bonded to a cyclic amide.
However, none of these documents suggests the effect of these compounds on the sigma receptor.
WO 2006/021462 and WO 2007/098964 describe pyrazole derivatives as selective inhibitors of the sigma receptor. These compounds present in the 3 position an alkoxy group.
There is still a need to find compounds that have pharmacological activity towards the sigma receptor, being both effective and selective, and having good “drugability” properties, i.e. good pharmaceutical properties related to administration, distribution, metabolism and excretion.